You should read chapter 9 in your STEM book on inferential statistics and write down any important points in your notebook. Remember – if you were running an experiment and could test everyone in the population the you would know your answer. Unfortunately, this is often not possible. So instead we test a sample of the population and we hope to be able to infer something about the whole population from the sample. But since there is always variability in the sample we choose, it can be difficult to know for sure if any differences we are seeing between our treatment and control groups are due to the treatment (independent variable) we applied or just due to chance. If we do see a difference between the experimental group and the treatment group, we can use mathematical tests to tell us the probability that the difference we are seeing is due to chance rather than due to our treatment. If the probability due to chance is sufficiently low, then we can start to suspect that our treatment is what actually made the difference. If the probability due to chance is too high, then our treatment was likely not the thing that made a difference. Chapter 9 discusses various statistical tests you can use to calculate this probability due to chance for various experiments and types of data. It also discusses what probability due to chance is considered too high to support your hypothesis that your treatment made a difference.